1. Field of the Invention
The present invention relates to an electronic endoscope that reduces radiation of extraneous emission noises.
2. Description of the Related Art
In recent years, for endoscope apparatuses including devices such as video processors that incorporate electronic circuits configuring image processing units or the like, there has been increasing need for measures against EMC (a generic term for EMI, a problem of giving electromagnetic interference, and EMS, a problem of receiving electromagnetic interference). In particular, in a field of medical equipment used in hospitals, EMC measures are necessary.
In an endoscope that inserts an elongated insertion portion into a body to observe an affected area or the like in the body, for example, a solid image pickup device such as a CCD is incorporated in a distal end portion of the insertion portion. An electrical signal photoelectrically converted by a solid image pickup device is transmitted to a video processor through a signal cable inserted in the insertion portion, an operation portion, and a universal cable. The video processor converts the transmitted electrical signal into a video signal and then outputs the video signal to a monitor apparatus.
Flexible tube portions of insertion portions and universal cables that configure endoscopes have flexibility. As shown in FIG. 1, a flexible tube portion and a universal cable are mainly composed of a laminated tube member (hereinafter, referred to as a corrugated tube) 100 configured by laminating a cover 101, a mesh-tube 102, and a helical tube 103. The cover 101 is insulating resin. The mesh-tube 102 is conductive tubular wire mesh and positioned inside the cover 101. The helical tube 103 is obtained by winding a strip-shaped conductive member into a spiral shape and positioned inside the mesh-tube 102.
In a conventional endoscope, at both ends of the corrugated tube 100, the cover 101 is scraped off so as to expose the mesh-tube 102. Then, the exposed mesh-tube 102 is electrically connected to a conductive corrugated tube connection member 110 so as to be electrically conductive with a metal member forming a sheath of the endoscope. Thereby, an unwanted current flowing through the sheath and causing an extraneous emission noise is fallen to the ground and an electromagnetic wave shielding property is established.
In order to achieve an inexpensive and small endoscope, the corrugated tube connection member 110 and the mesh-tube 102 may be adhesively secured to each other. However, if an adhesive for adhesively securing enters a gap between an inner circumferential face of the corrugated tube connection member 110 and an outer circumferential face of the mesh-tube 102 to form an adhesive layer 120, there arises a problem that electrical conductivity is impaired.
To solve the problem, as shown in FIG. 2, an adhesion portion 121 has been provided with a center O1 of the corrugated tube 100 being eccentric with respect to a center O2 of the corrugated tube connection member 110 and a part of the outer circumferential face of the mesh-tube 102 being in contact with the inner circumferential surface of the corrugated tube connection member 110, and the corrugated tube 100 and the corrugated tube connection member 110 have been adhesively secured to each other.
Also, in an endoscope apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2008-32801, a sixth embodiment indicates a thin-plate-shaped ring member in which a plurality of leaf spring pieces are provided and spaced apart from each other at regular distances. In the endoscope apparatus, a snap ring is screwed with a rear-end mouth ring and the leaf spring pieces are deformed radially inward as the snap ring rotates. Thereby, inside faces of the leaf spring pieces are brought into contact with an outer surface of a short tube to cause the short tube and the rear-end mouth ring to be conductive with each other.